Chip root analysis after machining carbon fiber reinforced plastics (CFRP) at different fiber orientations

Abstract

Machining carbon fiber reinforced plastics (CFRP) is currently being heavily investigated. The main drivers come from the aviation and automotive industry. Current drilling and milling tool geometries exhibit immense wear resulting in the damage of the work piece. Detailed understanding of chip formation mechanisms when machining CFRP is paramount and enables the optimization of tool geometries in terms of tool lifetime and work piece quality. Current knowledge about CFRP chip formation mechanisms is insufficient. Chip root experiments help understanding chip formation along the cutting edge and are well understood for the machining of metals [1,2]. Insufficient research has been performed in the field of chip formation processes when machining CFRP, especially on chip roots [3–5]. Unlike when machining metals, when machining CFRP micro-particles are generated as opposed to macro chips [4]. This fact makes it difficult to observe the CFRP chipping process, compared to metal machining. Furthermore CFRP is an anisotropic and inhomogeneous material causing machining properties to be highly dependent on the fiber orientation. This paper introduces an extensive study on CFRP chip roots for five different unidirectional fiber orientations using an orthogonal cutting test rig. Intentionally weakened work pieces have been produced. These work pieces enable truly representative cutting conditions due to a continuous cut and constant but wide range adaptable cutting speeds. Analyses of the chip roots are based on light microscopy (i), scanning electron microscopy (SEM) (ii) and micrographs (iii). In combination with previous studies in-house it qualifies to understand the wear mechanisms when machining CFRP. As a result fracture orientations, adhering abrasion particles, chip formation and chip movement allow for the understanding of CFRP chip formation.